yes
No, they are two completely different multiplayer setups.
Everything in Halo 4 as of now is co-op. Campaign, Spartan - Ops, and Infinity (Multiplayer) Internet, local, and system link.
Thank you based god.
yes it is in the multiplayer mode
yes
Yes you can play both Halo: CE and Halo 2 multiplayer on PC.
Indeed, Halo: Combat Evolved for the Xbox is multiplayer.
no you cannot
Multiplayer Map. Terminal.
No you can't.
Halo 2
Nothing. The multiplayer map-pack is an add-on. Which means you can't play the Multiplayer map pack without Halo 2. The only thing that is different is the maps, that get downloaded to your Xbox when you boot up the multiplayer map pack. The models, textures, gameplay is all exactly the same.